After you have had your first meeting, VCs may be slow to respond.  There are a few potential reasons for this.

First, (while processes vary by VC fund) it often takes a VC a week or more to discuss your venture with their partners.  Most venture firms hold their partner meetings on Mondays and they discuss new companies at those meetings.  So, if you met with the VC on a Tuesday it may take them a minimum of a week to respond.  However, if the partner that you met with is out of the office the following Monday or if the Monday partner meeting is cut short due to extraneous factors, it may take two weeks or longer for the VC to discuss the opportunity with their partners. Ultimately, a few weeks of waiting time does not necessarily mean that a VC is not interested.

Another reason why VCs may be slow to respond is because they are conducting some preliminary due diligence. If they have one key question about your business that they believe can be answered easily, they might first try to find out the answer before following up with you.  However, getting this answer can sometimes take a few weeks.  For example, if the VC has a contact with expertise in the field of question, it may take some time to get in touch with that individual if they are on vacation or otherwise inaccessible.  This process may seem especially slow, if the VC starts the diligence process after waiting to discuss the idea at the partner meeting.

Aside from the natural causes of delay, no response may also mean that there is a lack of VC interest. VCs are inundated with business plans and other managerial responsibilities.  As a result, only businesses that they are very interested in gain the momentum required for thorough exploration.  If the VC wasn't excited about your opportunity, even if it is a great business, your business may get lost in the shuffle.  Only the companies that VCs are most excited about seem to continuously float to the top.

In sum, be patient after the first meeting.  VCs will not move as quickly as you. However, you should do what you can to develop and maintain the interest of a VC so that they continue to evaluate your company.